Method and apparatus for managing packet congestion

ABSTRACT

A method and apparatus for addressing a congestion condition in a communication network are disclosed. For example, the method receives an alert for at least one of: a trunk or a Permanent Virtual Circuit (PVC), where the trunk or the PVC is associated with a route. The method determines whether the alert is associated with a congestion condition by determining whether a trunk utilization has exceeded a first predetermined threshold for the trunk or for the at least one trunk supporting the PVC. The method then rebuilds the route if the first predetermined threshold is exceeded for the trunk or for the at least one trunk supporting said PVC.

This application is a continuation of U.S. patent application Ser. No.11/763,950, filed Jun. 15, 2007, which is currently allowed and isherein incorporated by reference in its entirety.

The present invention relates generally to communication networks and,more particularly, to a method and apparatus for providing detection andprevention of packet congestion on networks such as the packet networks,e.g., Internet Protocol (IP) networks, Asynchronous Transfer Mode (ATM)networks, Frame Relay (FR) networks, etc.

BACKGROUND OF THE INVENTION

An enterprise customer may build a Virtual Private Network (VPN) byconnecting multiple sites or users over a network operated by atelephony or network service provider. For example, the enterprisecustomer's devices such as Customer Edge Routers (CERs) may be connectedto the network service provider's Layer 2 network through a ProviderEdge Router (PER). The Layer 2 network can be an Asynchronous TransferMode (ATM) network and/or a Frame Relay (FR) network. The voice and datapackets from the customer premise may traverse the Layer 2 network priorto reaching an IP network. For example, a virtual connection such as aPermanent Virtual Circuit (PVC) may be established for the customerthrough a Layer 2 network, e.g., an ATM network. However, the networkmay have to re-route a virtual connection due to network events such asfailures, maintenance activities, etc. Due to infrastructure build-outand cost limitations, the re-routes may result in less than optimalrouting. The customer traffic may experience increased latency, packetloss, trunk over utilization, etc.

SUMMARY OF THE INVENTION

In one embodiment, the present invention discloses a method andapparatus for addressing a congestion condition in a communicationnetwork. For example, the method receives an alert for at least one of:a trunk or a Permanent Virtual Circuit (PVC), where the trunk or the PVCis associated with a route. The method determines whether the alert isassociated with a congestion condition by determining whether a trunkutilization has exceeded a first predetermined threshold for the trunkor for the at least one trunk supporting the PVC. The method thenrebuilds the route if the first predetermined threshold is exceeded forthe trunk or for the at least one trunk supporting said PVC.

BRIEF DESCRIPTION OF THE DRAWINGS

The teaching of the present invention can be readily understood byconsidering the following detailed description in conjunction with theaccompanying drawings, in which:

FIG. 1 illustrates an exemplary network related to the presentinvention;

FIG. 2 illustrates an exemplary network for providing detection andprevention of packet congestion;

FIG. 3 illustrated an illustrative connectivity for trunk delaymeasurement;

FIG. 4 illustrates a flowchart of a method for providing detection andprevention of packet congestion;

FIG. 5 illustrates a flowchart of a method for determining excessivetrunk utilization; and

FIG. 6 illustrates a high-level block diagram of a general-purposecomputer suitable for use in performing the functions described herein.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures.

DETAILED DESCRIPTION

The present invention broadly discloses a method and apparatus forproviding detection and prevention of packet congestion. Although thepresent invention is discussed below in the context of ATM/FR and IPnetworks, the present invention is not so limited. Namely, the presentinvention can be applied for other networks, e.g., cellular networks andthe like.

FIG. 1 is a block diagram depicting an exemplary packet network 100related to the current invention. Exemplary packet networks includeInternet Protocol (IP) networks, Asynchronous Transfer Mode (ATM)networks, Frame-Relay networks, and the like. An IP network is broadlydefined as a network that uses Internet Protocol such as IPv4 or IPv6 toexchange data packets.

In one embodiment, the packet network may comprise a plurality ofendpoint devices 102-104 configured for communication with the corepacket network 110 (e.g., an IP based core backbone network supported bya service provider) via an access network 101. Similarly, a plurality ofendpoint devices 105-107 are configured for communication with the corepacket network 110 via an access network 108. The network elements 109and 111 may serve as gateway servers or edge routers (e.g., broadly as aborder element) for the network 110.

The endpoint devices 102-107 may comprise customer endpoint devices suchas personal computers, laptop computers, Personal Digital Assistants(PDAs), servers, routers, and the like. The access networks 101 and 108serve as a means to establish a connection between the endpoint devices102-107 and the NEs 109 and 111 of the IP/MPLS core network 110. Theaccess networks 101 and 108 may each comprise a Digital Subscriber Line(DSL) network, a broadband cable access network, a Local Area Network(LAN), a Wireless Access Network (WAN), and the like.

The access networks 101 and 108 may be either directly connected to NEs109 and 111 of the IP/MPLS core network 110 or through an AsynchronousTransfer Mode (ATM) and/or Frame Relay (FR) switch network 130. If theconnection is through the ATM/FR network 130, the packets from customerendpoint devices 102-104 (traveling towards the IP/MPLS core network110) traverse the access network 101 and the ATM/FR switch network 130and reach the border element 109.

The ATM/FR network 130 may contain Layer 2 switches functioning asProvider Edge Routers (PERs) and/or Provider Routers (PRs). The PERs mayalso contain an additional Route Processing Module (RPM) that convertsLayer 2 frames to Layer 3 Internet Protocol (IP) frames. An RPM enablesthe transfer of packets from a Layer 2 Permanent Virtual Connection(PVC) circuit to an IP network which is connectionless.

Some NEs (e.g., NEs 109 and 111) reside at the edge of the coreinfrastructure and interface with customer endpoints over various typesof access networks. An NE that resides at the edge of a coreinfrastructure is typically implemented as an edge router, a mediagateway, a border element, a firewall, a switch, and the like. An NE mayalso reside within the network (e.g., NEs 118-120) and may be used as amail server, honeypot, a router, or like device. The IP/MPLS corenetwork 110 may also comprise an application server 112 that contains adatabase 115. The application server 112 may comprise any server orcomputer that is well known in the art, and the database 115 may be anytype of electronic collection of data that is also well known in theart. Those skilled in the art will realize that although only sixendpoint devices, two access networks, and five network elements aredepicted in FIG. 1, the communication system 100 may be expanded byincluding additional endpoint devices, access networks, border elements,etc. without altering the present invention.

The above IP network is described to provide an illustrative environmentin which packets for voice and data services are transmitted onnetworks. An enterprise customer may build a Virtual Private Network(VPN) by connecting multiple sites or users over a network operated by atelephony or network service provider. The enterprise customer's devicessuch as Customer Edge Routers (CERs) may be connected to the networkservice provider's Layer 2 network through a Provider Edge Router (PER).The Layer 2 network can be an Asynchronous Transfer Mode (ATM) networkand/or a Frame Relay (FR) network. The voice and data packets from thecustomer premise may traverse the Layer 2 network from the PER towardsthe IP network. For example, a virtual connection such as a PermanentVirtual Circuit (PVC) may be established for the customer through aLayer 2 network, e.g., an ATM network, from the switch/routerfunctioning as the PER to the switch connected to the IP network.However, the network may have to re-route a virtual connection due tonetwork events such as failures, maintenance activities, etc.

For example, if a fiber cut occurs between two switches used to buildthe PVC, then the connection may have to be rerouted away from the fibercut. Due to infrastructure build-out and cost limitations, the re-routesmay result in less than optimal routing. For example, the primary routemight be the only direct connection between the two switches. In thatcase, any rerouting involves increasing the number of switches/nodes.This may also be referred to as “increasing the number of hops” betweenthe PER and the switch attached to the IP network. In turn, the customertraffic may experience increased latency, packet loss, trunk overutilization (excessive trunk utilization), etc. For example, if theoriginal topology provides two routes between the PER and the switchconnected to the IP network and traffic is normally divided evenlybetween the two routes, then the reroute may result in doubling of thetraffic on one route when a failure occurs on the other route. Thetrunks may then be over utilized, and a network alarm may be receivedfor an excessive trunk utilization, congestion, packet loss, increaseddelay, etc.

In one embodiment, the current invention provides a method for detectionand prevention of packet congestion. FIG. 2 illustrates an exemplarynetwork 200 in accordance with one embodiment of the current inventionfor detection and prevention of packet congestion. For example, acustomer may use the endpoint device 102 to obtain a service from anIP/MPLS core network 110. Traffic between the endpoint device 102 andthe IP/MPLS core network 110 may traverse the access network 101 and theATM/FR network 130. The endpoint device 102 is connected to an ATM/FRswitch 211 located in the ATM/FR network 130 through the access network101. The ATM/FR network 130 may contain a plurality of ATM/FR switches211-216. The ATM/FR switch 211 is functioning as a PER for the ATM/FRnetwork 130 for packets originated by customer endpoint device 102.Trunk 201 connects ATM/FR switches 211 and 212. Trunk 202 connectsATM/FR switches 212 and 213. Trunk 203 connects ATM/FR switches 213 and214. Trunk 204 connects ATM/FR switches 214 and 215. Trunk 205 connectsATM/FR switches 215 and 216. Trunk 206 connects ATM/FR switches 211 and216. The ATM/FR switch 214 is connected to the IP/MPLS core network 110through a border element 109. An illustrative Permanent Virtual Circuit209 is established/built connecting ATM/FR switches 211 and 214 overtrunks 201, 202 and 203 for providing a service to the customer endpointdevice 102. In turn, traffic from customer endpoint device 102 directedtowards IP/MPLS core network 110, traverses the ATM/FR network 130 usingthe permanent virtual circuit 207.

In one embodiment, a trunk monitoring module 231 is connected toswitches 211-216. The trunk monitoring module 231 is tasked withmonitoring the status of the trunks and PVCs. For example, when thetrunk monitoring module 231 receives an alert or a ticket, it notifiesthe application server 233. In turn, using the received notification(s),the service provider may implement a method for providing detection andprevention of packet congestion in the application server 233 as furtherdisclosed below.

In one embodiment, application server 233 may contain an automateddecision rules module for detecting and preventing packet congestion.Application server 233 is connected to an optimum route module 232.Application server 233 may utilize the optimum route module 232 torebuild routes. For example, the optimum route module 232 is capable ofobtaining topology information relating to the network and variousnetwork elements, e.g., switches, to provide one or more recommendedroutes between two points, e.g., between two switches. The optimum routemodule 232 may have access to routing information such as variousweights that are to be applied to various trunks, switches, and so on.As such, FIG. 2 illustrates that the ATM/FR switches 211 and 214 areconnected to the optimum route module 232 to support routing andrerouting.

In one embodiment, the application server 233 (the server with theautomated decisions rule module) is also connected to a ticketing system234, a notifications module 235 and a network topology system 236. Forexample, the service provider may store the network topology includingan association of PVCs, trunks, ports and switches (nodes) in thenetwork topology system 236. For example, PVC 207 may be associated withvarious ports on switches 211-214. The ticketing system 234 is forgenerating a ticket, if necessary, and the notifications module 235 isfor generating one or more notifications, e.g., a notification to anenterprise customer as to the detection of a congestion affecting thecustomer's service and its possible solution(s).

In one embodiment, upon receiving a notification from the trunkmonitoring module 231, the application server 233 may create a ticket(if one is not already created) and invokes the current method fordetecting and preventing packet congestion. For example, the applicationserver 233 analyzes (e.g., performing a correlation) the alarms/alertsand/or tickets to identify a trunk trouble type. If a trunk failurealarm or a packet loss alarm is received, then the method performs anATM/FR diagnosis. In one embodiment, an ATM/FR diagnosis may includemonitoring and checking ATM ports, ATM channels, facility alarms/events,performing tests for PVCs, and so on. If the ATM/FR diagnosis identifiesa network problem, then the method notifies the appropriate work centerthat handles the pertinent ATM/FR network troubles. Otherwise, themethod proceeds to determine whether or not an excessive trunk delay maybe the root cause for causing the congestion.

For example, if there is no trunk failure or packet loss due to anunderlying network failure, the method then determines whether or not aroute has exceeded a pre-determined number of switches/nodes. Forexample, a reroute function may have been performed that resulted in aroute traversing an excessive number of switches. In other words, anexcessive trunk delay may occur due to rerouting. If an excessive trunkdelay is detected (or a specific alert is received from another platformor a network element that is tasked with detecting packet congestion),then the method determines whether or not trunk utilization has exceededthe provisioned capacity. For example, an enterprise customer may haveexperienced an increase in business and may not have updated its networkcapacity, e.g., the enterprise customer may not have subscribed for aservice having a sufficient amount of throughput.

In one embodiment, the current method is able to determine the presenceof excessive trunk utilization by utilizing information pertaining toprovisioned capacity. For example, the present method may comparecommitted information rates (CIRs) for various customers with the actualobserved traffic volume on the affected trunk(s).

FIG. 4 illustrates a flowchart of a method 400 for providing detectionand prevention of packet congestion. For example, the service providermay implement the current method for detection and prevention ofcongestion in an application server, with an automated decision rulesmodule, e.g., by setting various thresholds. For example, the number ofswitches a packet is allowed to traverse in a Layer 2 network, a trunkdelay measurement, or a trunk utilization measurement may all havepredefined threshold settings. For example, a route for a packet may beconsidered excessive if it involves 9 switches or nodes. A trunk delaymay be considered excessive if it exceeds 80 ms. A trunk utilization maybe considered excessive if it exceeds 90%, and so on. Method 400 startsin step 405 and proceeds to step 410.

In step 410, method 400 receives an alarm or a ticket (broadly definedas an alert) indicating that there is a potential problem associatedwith a trunk or a PVC. For example, a customer may interact with aticketing system and reports that a PVC is degraded or down. In anotherexample, the trunk monitoring module 231 may receive an alert from aswitch indicating a problem with a particular trunk, and forwards thealert to the application server 233 being used for providing detectionand prevention of congestion. It should be noted that the received alertmay potentially indicate that a congestion condition may affect a routethat traverses over the reported trunk or a route that is traversed bysaid PVC.

In step 415, method 400 may optionally create a ticket, if a ticket isneeded. For the example above, the application server may create aticket for the trouble received from a switch through the trunkmonitoring module 231. The method then proceeds to step 420.

In step 420, method 400 may correlate the alarm and/or ticket toidentify the type of trunk trouble. For example, a ticket may have beencreated by a customer for a particular PVC, and the method may correlatethe ticket with one or more previously reported alarms that areassociated with a particular trunk failure or an event of packet lossthat would affect the particular PVC reported by the customer.

In step 425, method 400 determines whether or not an alarm is receivedfor a trunk failure and/or a packet loss. If a trunk failure alarm or apacket loss alarm is received, then the method proceeds to step 430 toperform an ATM/FR network diagnosis. Namely, since a trunk failure alarmor a packet loss alarm has been received, there is a possibility thatthe congestion is the result of an underlying network problem, e.g., aphysical failure of a link and so on. It should be noted that thepresent invention is not limited to any particular method of performingATM/FR network diagnosis. If a trunk failure alarm or a packet lossalarm is not received, then the method proceeds to step 440.

In step 430, method 400 performs an ATM/FR diagnosis. For example, themethod determines if a trouble may have been caused by a failure in aLayer 1 network, access network, etc. The method then proceeds to step435.

In step 435, method 400 determines whether or not an ATM/FR trouble isdetected. If an ATM/FR trouble is detected, then the method proceeds tostep 480 to refer the trouble to a work center that handles ATM/FRtroubles. Otherwise, the method proceeds to step 450 to perform a trunkdelay test.

In step 440, method 400 determines the number of switches that packetson the reported PVC are traversing from source towards theirdestination. For example, packets may traverse through an ATM/FR layer 2network over “x” number of switches.

In step 445, method 400 determines whether or not the number of switchesa packet is traversing, e.g., through an ATM/FR network, is in excess ofa pre-determined threshold. For the example above, the method determineswhether or not “x” is greater than nine. If the number of switches is inexcess of the threshold, the method proceeds to step 450. Otherwise, themethod proceeds to step 460.

In step 450, method 400 performs trunk delay tests. For example, themethod may send packets to measure round trip delay through one or moretrunks as discussed below. In one example, the method may use “ping”signals to various switches to determine trunk delays. The method thenproceeds to step 455.

In step 455, method 400 determines whether or not the measured trunkdelay is in excess of a predetermined threshold. For the example above,the method determines whether or not the trunk delay is greater than 80ms. If the trunk delay is in excess of the predetermined threshold, thenthe method proceeds to step 465 to perform a trunk utilization test.Otherwise, the method proceeds to step 460.

In step 460, method 400 determines whether or not a congestion alert isreceived. Namely, additional alerts can be received that may potentiallyindicate or substantiate a congestion condition. For example, theswitches/routers may contain real time counters for tracking discardedpackets, thereby allowing the switches/routers to provide congestionnotifications. In one example, the congestion alerts may be BackwardExplicit Congestion Notifications (BECNs) and/or Forward ExplicitCongestion Notifications (FECNs). Thus, it is contemplated that acongestion condition can be explicitly made know to the applicationserver 233 by a network element. If one or more congestion alerts arereceived, then the method proceeds to step 465. Otherwise, the methodproceeds to step 480 to notify an appropriate work center of a trouble.

In step 465, method 400 performs a trunk utilization test for thereported alert. For example, one or more trunks supporting the reportedPVC are measured to determine the actual usage of the trunks by thecustomer. Namely, the measured utilization rate may be in excess of aCommitted Information Rate (CIR) for the customer. The method thenproceeds to step 470.

In step 470, method 400 determines whether or not the trunk utilizationis in excess of the provisioned capacity, CIR. If the trunk utilizationis in excess of the provisioned capacity, then the method proceeds tostep 475. Otherwise, the method proceeds to step 480 to notify anappropriate work center of a trouble.

In step 475, method 400 locates and rebuilds an optimal route for thetraffic. For example, if a PVC is traversing a long route, it may bererouted using other switches (and/or trunks) on a shorter route. Itshould be noted that although rebuilding the route may involve providinga completely different route, that is not always the case. For example,in one embodiment, additional resources can be given or allocated to thenetwork elements and/or trunks supporting the customer's PVC. Forexample, a second customer's PVC can be rerouted to another route,thereby freeing up capacity for the first customer's PVC. The methodthen proceeds to step 480.

In step 480, method 400 determines the work center for a particular typeof trouble, refers the trouble accordingly, notifies the affectedcustomer(s) and closes ticket. In one embodiment, if the congestiondetected by the method 400 has been resolved by rebuilding a route forthe customer's PVC, then the present method may notify the affectedcustomer that a congestion has been detected and resolved automaticallyby the service provider. In doing so, the service provider may notifythe customer that the congestion was the result of the customerexceeding the provisioned capacity, CIR. The service provider can theninvite the customer to upgrade its current service to address theunder-provisioned capacity problem. This approach allows a customer tobe immediately notified of its additional needs to address the detectedcongestion condition, thereby increasing customer satisfaction and toprovide the service provider with new opportunities to provideadditional services (e.g., a service upgrade) to existing customers whoare outpacing their current subscribed services. The method then returnsto step 410 to continue receiving additional alerts or ends in step 490.

As discussed above, a trunk utilization test can be performed where acustomer's actual usage for each trunk can be measured and tracked overtime. However, this approach can be computationally expensive in certainapplications, e.g., where the trunk is utilized by a large number ofdifferent customers, where large number of packets must be analyzed andcategorized.

In one embodiment, the current invention may determine excessive trunkutilization very quickly by performing a trunk utilization test on twotypes of traffic via the trunk monitoring module 231. For example, thetypes of traffic are selected such that, one type of traffic is likelyto be impacted by excessive trunk utilization while the other type oftraffic is not likely to be impacted by excessive trunk utilization. Forexample, the method may measure roundtrip trunk delays as describedbelow for Constant Bit Rate (CBR) traffic and Variable Bit Rate (VBR)traffic. VBR traffic is likely to be impacted by excessive trunkutilization, and the impact may be observed as an increase in trunkdelay and/or loss. In contrast, CBR traffic (assuming it is not bursty)is not impacted by excessive trunk utilization. Furthermore, if there isan underlying network problem, e.g., a fiber cut has occurred and trunkshave been rerouted, then both CBR traffic and VBR traffic will beimpacted and the trunk delay and/or loss measurements may increaseequally for both.

In one embodiment, the current method measures roundtrip trunk delay byfirst setting up two predefined (e.g., preferred) Permanent VirtualCircuits (PVCs) over a shared predefined path with one PVC being onetrunk longer than the other PVC. FIG. 3 illustrated an illustrativeconnectivity for trunk delay measurement. For example, trunk 201connects switches 211 and 212. Trunk 202 connects switches 212 and 213.Trunk 203 connects switches 213 and 214. A PVC 301 is established/builtconnecting switches 211 and 213 over trunks 201 and 202. A PVC 302 isestablished/built connecting switches 211 and 214 over trunks 201, 202and 203. Test traffic is then injected in both PVCs 301 and 302 and theroundtrip time is measured. Since the PVCs share trunks 201 and 202, theroundtrip delay for trunk 203 may be derived by subtracting theroundtrip time of PVC 301 (the shorter PVC) from the roundtrip time ofPVC 302 (the longer PVC). Similarly, the roundtrip delay for trunk 202may be measured by setting up one PVC over trunks 201 and 202, and asecond PVC over trunk 201 alone. Note that the roundtrip delays aremeasured for two types of traffic, namely CBR traffic and VBR traffic.

In one embodiment, the service provider may build different pairs ofPVCs for the two types of traffic. In another embodiment, the serviceprovider injects different types of traffic on the same pairs of PVC atdifferent times and measures trunk delay for each type of traffic. Inone embodiment, the service provider performs the trunk delaymeasurements in a predetermined interval, e.g., every 15 minutes, 30minutes, etc., to detect increases in trunk utilization. The trunkmonitoring module 231 may then measure trunk delays for CBR traffic andVBR traffic, and determines whether or not an observed trunk delay isdue to excessive trunk utilization. Broadly, the trunk monitoring module231 may determine whether an excessive trunk utilization conditionexists in a trunk.

In one embodiment, the service provider is able to associate aparticular trunk delay with an estimated level of trunk utilization.This association can be constructed by sending a certain amount oftraffic onto each trunk and then measuring the trunk delay. Thisapproach can be repeated by incrementally increasing the amount oftraffic placed onto the trunk until the capacity of the trunk iscompletely used, thereby providing an association between trunk delaywith an estimated level of trunk utilization. This process can berepeated for each type of traffic as well, e.g., CBR traffic and VBRtraffic and the like. It should be noted that association between trunkdelay with an estimated level of trunk utilization may be different fordifferent types of traffic.

When an excessive trunk utilization is detected, the trunk monitoringmodule 231 may create an alert/alarm and forwards it to the applicationserver 233 with automated decision rules for handling congestionsituations. For example, the application server may then use the trunkutilization information to reroute traffic as needed for a particularPVC.

FIG. 5 illustrates a flowchart of a method 500 for determining excessivetrunk utilization. For example, the trunk monitoring module 231 mayimplement the method 500 to determine excessive trunk utilization byperforming trunk delay measurements on Constant Bit Rate (CBR) trafficand Variable Bit Rate (VBR) traffic. Method 500 starts in step 505 andproceeds to step 510.

In step 510, method 500 selects a trunk whose trunk delay is to bemeasured. For example, the method selects a trunk between two switches.The method then proceeds to step 515.

In step 515, method 500 sets up two predefined (preferred) PermanentVirtual Circuits (PVC) over a shared path with one PVC being shorterthan the other PVC by the selected trunk. For example, If trunk “C” isselected, one PVC may contain trunks “A”, “B”, and “C” while the shorterPVC contains trunks “A” and “B.” The trunk selected in step 510 is notshared by the two PVCs while all other trunks are shared.

In step 520, method 500 transmits (or inserts) test traffic in both PVCsand measures roundtrip delay (time) for constant bit rate traffic andvariable bit rate traffic. In one example, the method may insertconstant bit rate traffic in both PVCs, and measures the roundtrip timefor constant bit rate traffic. In another example, the method may insertvariable bit rate traffic in both PVCs, and measures the roundtrip timefor variable bit rate traffic. For the example above, the roundtripdelay for the shorter PVC is for traversing to a switch over trunks “A”and “B” and back to the source. The roundtrip delay for the longer PVCis for traversing to a switch over trunks “A”, “B”, and “C” and back tothe source.

In step 525, method 500 determines a trunk delay. For example, themethod subtracts the roundtrip delay of the shorter PVC from that of thelonger PVC to determine the trunk delay for the selected trunk, i.e.,for the trunk that is not shared. For the example above, the trunk delayfor trunk “C” is determined by subtracting the delay for traversing onlytrunks “A” and “B” from the delay for traversing the trunks “A”, “B”,and “C.”

Note that the roundtrip delays are measured for the two types oftraffic, namely CBR traffic and VBR traffic separately. If the same PVCsare used for roundtrip delay measurements for both types of traffic, themethod performs delay measurements for each type of traffic and recordsthe results.

In step 530, method 500 analyzes the trunk delays for the two types oftraffic, e.g., CBR traffic and VBR traffic. For example, the methoddetermines if only one type of traffic is experiencing trunk delay orboth types of traffic are experiencing trunk delay. For example, thetrunk delay for a CBR may not be excessive while that of a VBR may beexcessive.

In step 535, method 500 determines whether or not an observed trunkdelay is due to excessive trunk utilization. For example, a serviceprovider may set a trunk utilization of 90% of the capacity of the trunkas being excessive. In turn, if the measured trunk delay for thevariable bit rate traffic indicates a substantial increase (e.g.,greater than 50%) in trunk delay for variable bit rate traffic with aminimal increase in trunk delay for the constant bit rate traffic (e.g.only 1%), then method 500 may determine that the observed trunk delay(s)is due to excessive trunk utilization. It should be noted that the aboveexample is premised on the assumption that the 50% increase in trunkdelay for variable bit rate traffic coupled with the 1% increase intrunk delay for the constant bit rate traffic are associated ortranslated as being greater than a trunk utilization of 90% of thecapacity of the trunk.

In one embodiment, it is noted that VBR traffic can be impacted byexcessive trunk utilization, and the impact may be observed as anincrease in trunk delay and/or loss. Whereas, CBR traffic is notsignificantly impacted by excessive trunk utilization. However, if thereis an underlying network problem, e.g., a fiber cut that has occurredwhere trunks have been rerouted, then both CBR traffic and VBR trafficmay be significantly impacted and the trunk delay measurements mayincrease for both. Under this scenario, method 500 may determine thatthe observed trunk delay(s) is not due to excessive trunk utilization.In step 535, if excessive trunk utilization is detected for a trunk,then the method proceeds to step 540. Otherwise, the method returns tostep 510.

In step 540, method 500 notifies the application server 233 thatexcessive trunk utilization has been detected for a trunk. For example,the service provider may have implemented the application server 233 forreceiving trunk utilization alerts to invoke a rerouting function forreducing trunk utilization rates. In other words, the method 500 maynotify the application server such that mitigation steps for reducingcongestion may begin immediately as discussed above in FIG. 4. Themethod then returns back to step 510 to continue performing trunkutilization measurements or ends in step 550.

It should be noted that although not specifically specified, one or moresteps of methods 400 and 500 may include a storing, displaying and/oroutputting step as required for a particular application. In otherwords, any data, records, fields, and/or intermediate results discussedin the method can be stored, displayed and/or outputted to anotherdevice as required for a particular application. Furthermore, steps orblocks in FIGS. 4 and 5 that recite a determining operation or involve adecision, do not necessarily require that both branches of thedetermining operation be practiced. In other words, one of the branchesof the determining operation can be deemed as an optional step.

FIG. 6 depicts a high-level block diagram of a general-purpose computersuitable for use in performing the functions described herein. Asdepicted in FIG. 6, the system 600 comprises a processor element 602(e.g., a CPU), a memory 604, e.g., random access memory (RAM) and/orread only memory (ROM), a module 605 for providing detection andprevention of packet congestion on networks or for determining excessivetrunk utilization, and various input/output devices 606 (e.g., storagedevices, including but not limited to, a tape drive, a floppy drive, ahard disk drive or a compact disk drive, a receiver, a transmitter, aspeaker, a display, a speech synthesizer, an output port, and a userinput device (such as a keyboard, a keypad, a mouse, and the like)).

It should be noted that the present invention can be implemented insoftware and/or in a combination of software and hardware, e.g., usingapplication specific integrated circuits (ASIC), a general purposecomputer or any other hardware equivalents. In one embodiment, thepresent module or process 605 for providing detection and prevention ofpacket congestion on networks or for determining excessive trunkutilization can be loaded into memory 604 and executed by processor 602to implement the functions as discussed above. As such, the presentmethod 605 for providing detection and prevention of packet congestionon networks or for determining excessive trunk utilization (includingassociated data structures) of the present invention can be stored on acomputer readable medium or carrier, e.g., RAM memory, magnetic oroptical drive or diskette and the like.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. Thus, the breadth and scope of a preferred embodiment shouldnot be limited by any of the above-described exemplary embodiments, butshould be defined only in accordance with the following claims and theirequivalents.

What is claimed is:
 1. A method for addressing a congestion condition ina communication network, comprising: receiving, via a processor, analert for a trunk associated with a route; determining, via theprocessor, whether the alert is associated with the congestion conditionby determining whether a trunk utilization has exceeded a firstpredetermined threshold for the trunk; measuring, via the processor, atrunk delay for variable bit rate traffic and a trunk delay for constantbit rate traffic, when the trunk utilization exceeds the firstpredetermined threshold; determining, via the processor, that the trunkutilization is excessive when the trunk delay for the variable bit ratetraffic exceeds a second predetermined threshold and the trunk delay forthe constant bit rate traffic does not exceed a third predeterminedthreshold; and rebuilding, via the processor, the route when the firstpredetermined threshold is exceeded for the trunk and when the trunkutilization is determined to be excessive, wherein the rebuilding theroute comprises providing additional resources to the route.
 2. Themethod of claim 1, further comprising: notifying a customer that thecongestion condition affects a network service of the customer.
 3. Themethod of claim 2, further comprising: offering a service upgrade to thecustomer to address the congestion condition.
 4. The method of claim 1,wherein the alert comprises a backward explicit congestion notification.5. The method of claim 1, wherein the alert comprises a forward explicitcongestion notification.
 6. The method of claim 1, further comprising:determining whether the alert is associated with a packet loss alarm;and determining whether the alert is associated with an asynchronoustransfer mode network/frame relay network trouble if the alert isassociated with the packet loss alarm.
 7. A non-transitorycomputer-readable medium storing instructions which, when executed by aprocessor, cause the processor to perform operations for addressing acongestion condition in a communication network, the operationscomprising: receiving an alert for a trunk associated with a route;determining whether the alert is associated with the congestioncondition by determining whether a trunk utilization has exceeded afirst predetermined threshold for the trunk; measuring a trunk delay forvariable bit rate traffic and a trunk delay for constant bit ratetraffic, when the trunk utilization exceeds the first predeterminedthreshold; determining that the trunk utilization is excessive when thetrunk delay for the variable bit rate traffic exceeds a secondpredetermined threshold and the trunk delay for the constant bit ratetraffic does not exceed a third predetermined threshold; and rebuildingthe route when the first predetermined threshold is exceeded for thetrunk and when the trunk utilization is determined to be excessive,wherein the rebuilding the route comprises providing additionalresources to the route.
 8. The non-transitory computer-readable mediumof claim 7, further comprising: notifying a customer that the congestioncondition affects a network service of the customer.
 9. Thenon-transitory computer-readable medium of claim 8, further comprising:offering a service upgrade to the customer to address the congestioncondition.
 10. The non-transitory computer-readable medium of claim 7,wherein the alert comprises a backward explicit congestion notification.11. The non-transitory computer-readable medium of claim 7, wherein thealert comprises a forward explicit congestion notification.
 12. Thenon-transitory computer-readable medium of claim 7, further comprising:determining whether the alert is associated with a packet loss alarm;and determining whether the alert is associated with an asynchronoustransfer mode network/frame relay network trouble if the alert isassociated with the packet loss alarm.
 13. An apparatus for addressing acongestion condition in a communication network, comprising: aprocessor; and a non-transitory computer-readable medium storinginstructions which, when executed by the processor, cause the processorto perform operations, the operations comprising: receiving an alert fora trunk associated with a route; determining whether the alert isassociated with the congestion condition by determining whether a trunkutilization has exceeded a first predetermined threshold for the trunk;measuring a trunk delay for variable bit rate traffic and a trunk delayfor constant bit rate traffic, when the trunk utilization exceeds thefirst predetermined threshold; determining that the trunk utilization isexcessive when the trunk delay for the variable bit rate traffic exceedsa second predetermined threshold and the trunk delay for the constantbit rate traffic does not exceed a third predetermined threshold; andrebuilding the route when the first predetermined threshold is exceededfor the trunk and when the trunk utilization is determined to beexcessive, wherein the rebuilding the route comprises providingadditional resources to the route.
 14. The apparatus of claim 13,further comprising: notifying a customer that the congestion conditionaffects a network service of the customer.